LED epitaxial structure and manufacturing method

Abstract

An LED epitaxial structure includes a substrate, a buffer layer and an epitaxial layer. The buffer layer is grown on a top surface of the substrate, and the epitaxial layer is formed on a surface of the buffer layer. The epitaxial layer has a first n-type epitaxial layer and a second n-type epitaxial layer. The first n-type epitaxial layer is formed between the buffer layer and the second n-type epitaxial layer. The first n-type epitaxial layer has a plurality of irregular holes therein.

What is claimed is: 
     
       1. A method for manufacturing an LED epitaxial structure, includes steps:
 providing a substrate; 
 providing a buffer layer grown on a top surface of the substrate; 
 a first n-type epitaxial layer being doped and grown on a top surface of the buffer layer, the first n-type epitaxial layer being doped and grown with a high doping concentration gradually decreasing to a low doping concentration from a bottom surface to a top surface of the first n-type epitaxial layer; 
 immerging the first n-type epitaxial layer to form a plurality of irregular holes with wet etching; 
 and a second n-type epitaxial layer, and an active layer, and a p-type epitaxial layer being grown sequentially on the first n-type epitaxial layer. 
 
     
     
       2. The method for manufacturing the LED epitaxial structure of  claim 1 , wherein the highly doped concentration gradually decreases to the low doped concentration, and the highly doped concentration is near the buffer layer. 
     
     
       3. The method for manufacturing the LED epitaxial structure of  claim 1 , wherein the first n-type epitaxial layer deposited on the buffer layer of substrate is immerged into an oxalic acid solution. 
     
     
       4. The method for manufacturing the LED epitaxial structure of  claim 3 , wherein the wet etching is a bias-assisted wet etching, the oxalic acid solution is applied bias, and an electric field is produced. 
     
     
       5. The method for manufacturing the LED epitaxial structure of  claim 1 , wherein the highly doped concentration is 10 19  and the low doped concentration is 10 18 .